Non-Patent Document 1 depicts a gravity feeder in FIG. 7.40 and describes “In order to achieve uniform filling, empirically known is that it is important to appropriately set a ratio of a new material and an old material having circulated in a feeder and uniformly mix these materials.” It is well known that mixing a material leaked out of a die onto a rotating die table and recovered with a new material (powdery material) and uniformizing these materials are important in tableting by compression molding.
This document never describes specifically how to recover the material and how to uniformly mix the new material and the recovered material. In other words, Non-Patent Document 1 fails to describe any specific recovering means and any uniformly mixing means. Furthermore, on the basis of the expression “circulated”, the technique described in Non-Patent Document 1 can be regarded as being applicable to a case where, in the rotary compression molding machine, a single type of powdery material is supplied and compressed and as being related to a common technique for circulating the single type of powdery material and recovering the powdery material on a rotating die table.
In a case where there are a plurality of powdery material supply devices in order to produce multi-layer tablets or multi-layer products, such a technique is not applicable to the means for circulating a powdery material and recovering the powdery material on a rotating die table because a plurality of powdery materials are mixed together.
Patent Document 1 relates to the invention of “a shoe box in a powdery material molding device” and clearly discloses a method of sucking and recovering a powdery material leaked out of the shoe box (i.e., feed shoe) corresponding to the powdery material filling device in this application. Such recovery by suction, in other words, the method using air causes segregation of particles configuring a powdery material due to particle diameters or specific gravity. This method is not applicable to a case where segregation seriously influences the quality such as non-uniformity of medicinal properties contents (drug contents) as in mixed powdery materials used for molding tablets containing medicinal properties.
Patent Document 2 relates to the invention of “a method and device of molding a powdery material” and describes, in FIG. 3 for example, a method of returning an unnecessary pre-molded product directly to a cavity (corresponding to a “feeder” in this application) by operating a powdery material returning pusher. However, this document does not relate to recovery of a leaked powdery material but merely describes pushing the pre-molded product in a conventional technique so as to return the pre-molded product again into the feeder with the push force. When the pre-molded product is returned directly, a molded product is molded again from a material including a powdery material and the pre-molded product mixed together. In this case, it is impossible to achieve homogenization and prevent segregation of the powdery material.
As described above, all of these conventional techniques relate to compression molding of a single type of powdery material and are not applicable to a case where a rotary compression molding machine having a plurality of feeders produces a molded product by compressing and molding a plurality of types of powdery materials.